Treatment of crude wax



29 M5@ l P. H. Rica-1ER ET AL @8599432 TREATMENT oF CRUDE WAX Filed Dec. 29, 1955 W @if 1Mo/UNG M P 'rv .l Rather' nited States` TREATMENT OF CRUDE WAX Pedro H. Richer and Eugene J. Reeves, Beaumont, Tex., assignors to Socony Mobil @il Company, lne., New York, N. Y., a corporation of N ew York Application December 29, 1955, Serial No. 556,235

5 Claims. (Cl. 196-20) This invention relates to the treatment of crude petroleum wax. More particularly, the present invention is concerned with an improved process Vfor removing oil from la `crude mixture of solid waxy hydrocarbons and effecting separation of the `same into a low melting point wax and a high melting point wax.

In the usual reiining of petroleum, the .crude is subjected to distillation, separating it into :a number of fractions of varying vol-atilities and viscosities. The fraction ordnarily referred to las parai'lin distillate, which, in general, is a fraction having a bo-iling range of about 340 F. to about 590 F., when distilled under an absolute pressure of millimeters of vmercury and which ordinarily is obtained from parai'linic Vbase and mixed -base crudes, is separated into `a solid wax fraction and a liquid oil fraction. Such separation or dewaxing may be xaccomplished by diluting the paraffin distillate with an appropriate solvent which is miscible with V4the oil but immiscible with ,the wax, chilling the resulting mixture and iilter pressing. Alternatively, the desired separation may be effected by various centrifugal processes, so-called cold settling processes and the like. The solid fraction so obtained is ordinarily referred to as slack wax and still contains a considerable quantity of oil of the order of 50 percent or more by weight.

This oil may be removed by :any of `a number of methods, such las by subjecting the slack wax to ia sweating operation which `consists essentially of fractionally melting and draining the oil `and lower melting waxes from higher melting waxes. Another method employed is the solvent deoiling process in which -a suitable solvent as, for example, a liquefied normally gaseous hydrocarbon, Ibenzol, acetone, and the like is used. In such method, the Asolvent is usually :added to the waxy charge `and the resulting mmture is then chilled. The waxy constituents which separate out are ordinarily removed from the dewaxed oil by filtration. The resulting wax cake may be washed with a suitable solvent, such as naphtha, in order to further reduce the amount of oil in the wax. Still another deoiling method currently practiced is the emulsion process in which the wax charge is mixed with a non-viscous non-solvent while in the molten state, after which it is cooled to -congeal the wax. The congealed wax is ythen separated from the oil in non-solvent emulsion -by means of a basket `type centrifuge lined with ya filter material.

The crude hydrocarbon wax resulting from the above various processes will usually consist of oil, low melting point wax and .high melting point wax. The proportions of these various constituents and the characteristics of the various oils `and waxes contained in the crude wax will vary greatly depending on the original stock which has been dewaxed, the treatment which has been given this stock prior to the dewax-ing process, `and the particular dewaxing and deoiling process used. Usually, however, the oil content of the crude wax will be relatively small and `generally within the lapproximate range of 2 to l0 percent by weight. In general, the waxes thus Patented Sept. 2, 1958 removed may be classified tas petrolatum waxes which have relatively high melting points, generally within the `approximate range of 145 F. to 170 F. `and parafn waxes consisting of commercially high melting point waxes, for instance, those melting at `.about 135 F. to about 150 F. `and .the relatively low melting point waxes, for instance, those melting below about F.

it is `a major object of the present invention to refine such crude wax and particularly to separate the same in an ecient manner, into its respective components.

The above and other objects which will be :apparent to those skilled in the fart are attained in accordance with the process of this invention, which comprises subjecting a charge of the above-described crude hydrocarbon wax to distillation under non-cracking conditions, removing as overhead la fraction of low melting point, low boiling point wax, removing as a separate fraction a higher boiling distillate containing high melting point paraffin wax, solvent deoiling the latter fraction to yield .a high melting point parain wax land la nitrate, combining the liltrate from said deoiling with the aforementioned overhead fraction `and solvent deoiling the resulting mixture to separate a low melting point paraffin wax therefrom.

ylt has been found, in accordance with the present invention, that the addition of low melting point, low boiling point overhead waxes to the filtrate result-ing from lsolvent deoiling of lthe distillation heart-cut waxes enables 'an efiicient separation of high melting and low melting waxes to be made. lt has been discovered that the resulting mixture of overhead waxes and filtrate when subjected to solvent deoiling has an appreciably greater filtration rate than that secured upon solvent deoiling the filtrate waxes alone. Thus, the filtration rote of the Iabove resulting mixture, following the process of this invention, is increased several-fold over the rate of filtration obtained at lcomparable wax oil content with the iil trate waxes alone.

T-he distillation step of the present process is carried out under conditions characteristic of sub-atmospheric di-still-ation, i. e., vacuum distillation or distillation with steam or other suitable inert gas. The distillation is effected under conditions which avoid cracking of the crude wax charge. Thus, the distillation is desirably carried out Ibelow cracking temperatures, i. e., bel-ow about 650 F. yand preferably between about 500 F. `and about 600 F. When vacuum distillation is employed, it is preferred that the :absolute pressure be in the order of 5 to 10 millimeters of mercury, and when steam distillation is ernployed, it is preferred that sufficient steam lbe used to provide from 1 to 2 volumes of condensed water per volume of distillate taken off.

The fractions are separated ordinarily on the basis of the average melting point of the waxes produced by deoiling the distillates. In accordance with the present invention, the crude wax charge is separated into two distillate fractions and a residual or bottoms fraction. The lower boiling distillate overhead fraction upon combinatio-n with the ltrate from solvent deoiling of the higher boiling distillate and subsequent deoiling of the mixture yields a low melting point wax, i. e., a wax having a melting point below about 130 F. and generally in the approximate range of 120 F. to 130 F. The higher boiling distillate fraction upon deoiling yields a high melting point wax, i. e one generally having a melting point in the approximate range of F. to 150 F.

In carrying out the improved process of the present invention, the various deoiling operations of the products resu'iting from distillation of the crude wax are accomplished in the presence of solvents Vor diluents including, for exampie, ketones, such as acetone, methyl ethyl ketone, methyl pro-pyl ketone, methyl iso'outyl ketone, etc.; aromatic hydrocarbons, such as benzene and toluene; alcohols, such as ethyl alcohol, isopropyl alcohol, normal propyl alcohol, and the like; petroleum naphthas;

Yhalogenated hydrocarbons, such as ethylene Ydichloride and Vchloro diiiuoromet'hane, or mixtures thereof. The normally gaseous diluents serve to dilute and also to chill the mixture when the diluent'is evacuated under reduced pressure. Ordinarily, mixtures of solvents or diluents such as toluene Vand methyl ethyl ketone are employed. It will be understood that the solvent employed is a preferential solvent p for and miscible with the oil While being immiscible with the wax.

T heV solvent deoiling steps can be carriedV out by various known methods wherein the primary object of the step is to obtain a substantially completelyoil-free wax. Preferably, the wax is mixed with at least a substantialportion of the solvent or diluent, such as at least 1 to 4 volumes of solvent per volume of wax. Then the mixture is preferably heated to about 20 F. to 50 F. above the average melting point of the wax material. During the subsequent chilling of the solvent-wax-oil mixture, additional solvent, such as l to l or more volumes per volume of 'waxrcharge, can be added as desired. After the mixture has been cooled to the proper wax deoiling temperature, i.V e., about 0 F. to 60 F.,'the oil-free wax is separated in a suitable manner, 'such as by means of a continuous iilter. preferably less than 0.5 percent oil.

Distillation of the low melt waxes into an overhead fraction in accordance with the present process minimizes processing these waxes through the high melt wax cycle. Generally, an overhead fraction of from 1 to 50 percent by volume, and preferably from about l0 to about 30 percent by volume,will be utilizedV Vin processing the crude hydrocarbon wax; Distillation may be carried out so that substantially no residue is obtained or residual wax, if any, remaining after the distillation may be deoiled either separately or in mixturewith the distillation overhead and the filtrate from' the high melt waxprocessing. VDeoiling ofthe mixture is preferred since plant operations are thereby simplified by reducing the number of products handled. Y i

The method of the inventionV is illustrated in simplified vdiagrammatic form in the attached drawings wherein:

Figure l'shows one embodiment of the process of the invention.

Figure 2 shows a second and generally preferred embodiment of the process of the invention.

Referring more particularly to Figure l, theV charge of crude Vhydrocarbon wax is introduced into.,distillation column 'through conduit 171. AY low boiling, low meltkingparailin waxrpasses overhead through conduit 12.

Arhigh melting paraiiin wax distillate'passes through con- .duit;13 to solvent deoiling unit 14. High melting point Wax is withdrawn via conduit 15 and the filtrate resulting Y Yfrom such 'deoiling is withdrawn through conduit 16. The

latter is combined with the overhead distillate iiowing through conduit 12 and the resulting mixture is conduced i to solvent deoiling unit 17 wherein low melting point wax deoiling unit 21 from which deoiled residual Ywax is with- Y drawn through outlet 22 and the separatedV oil is removed through Voutlet 23. TurningV now to the procedure shown in Figure 2, the

Y' charge of crude hydrocarbon wax isintroduced into distillation column 30 through conduit 31. A low boiling,

low melting paraffin wax passes overhead through conduit j32. Y Ahigh melting parain wax` distillate passes through 2,850,432 Y, e e

The wax product contains less than 1 percent,

These distillation fractions conduit 33 to solventdeoiling unit 34. High melting point s wax is withdrawn from such unit through conduit 35 and the filtrate resulting from such deoiling is Withdrawn through conduit 36. The latter is combined with the overhead distillate owing through 32 and residual Ywax remaining from the distillation owing through conduit 37. The resulting mixture is conducted to solvent deoiling unit 38 wherein low melting point Wax is Yseparated and withdrawn through outlet 39 and separated oil is removed through outlet 40.

Typical results obtained in accordance with the present process are as follows: i

A crude hydrocarbon wax having a melting point (ASTM) of 130 F. and an oil Vcontent of 3.9 percent'byV weight was fractionated at a pressure of l0 mm. of mercury to obtain 0-87, l3L87, 43.5-87, and 87-100% volume cuts. Physical characteristics of the crude Wax fractions so obtained are shown in the following Table I:

Table I v Di'stillation fractions Position in charge 0-87 13-87 26-87 43. 5-87 87-100 Yield, percent vol. charge 87 Y 74 61 43. 5

Properties of fractions; Y

' Gravity, API 42. 3 42. 8 42. 5 41. 7 38.0 Meltiug p0` t, F., ASTM--- 130 131 133 134 147 Oil content, percent weight- 3. 7 3. 0 2. 9 2. 7 ,7.1 Distillation at 10 mm.-

I. B. P f Y F-- 388 e 428 432 446 486 10%- 452 472 486 488 564 20%. 468 486 506 510 572 30%- 488 494 510 518V 584 40,f 498 504 516 y 522 690k 50%. V510 512 524 526 604 60%- V51S 522 530 528 612 p 70%- 526 530V 538 532 620 80%. 538 538 546 540 625 90%. 552 550 554 556 E. 594 598 596 Y 594 Y15 `to l, and removing the resulting deoiledl wax on aV rotary filter. Yields, melting points, and'oil contents of the deoiled waxes aresset forth in Table 11 below:

Table II Wax yield, percent Wax properties Distillation frac- Deoiling ,Y Y tionineharge, Y temp., Melting Oil percent vol. F. Charge Overall l point, content', F., weight.

ASTM percent 2o ss 72 133 i o. 0 8, V4.o 72 es 13s o. 50 63 55 138 0. 60 48 42 141 0. 20 Y 83 61 135 0. 13-87 40r Y7s Y 54 13s o. V60 49 36 142 0. 51 137 0. 4S 138 0. 26-87 4o 74 45 139 o. f Y 60 55 34 144 0. 1 2o 83 36 139 o. V43.5--87 40V 75 33 141 Y 0. Y 60 57' 25 145 0. 20 82 11 150 0. 87-100 40 72 9 153 0. s f J Y 60 60 8 158V 0.

lBased on crude Wax.

LowV melting point waxes' are availablein the ltrateY withV the distillation overhead and with the distillationV overheadY and bottomsV were deoiled at temperatures varywereV deoiled at temperaing from 0 F. to 40 F. with a solvent of 40 percent ing point paraffin wax and a filtrate, admixing said 'filtrate volume toluene and 60 percent volume methyl ethyl with the aforementioned overhead and solvent deoiling ketone. Yields and melting points of the waxes obtained the resulting mixture to separate a low melting point are presented in Table III below: parafiin wax therefrom.

Table III High melt Wax filtrate source Low melt wax components Filtrate yield High melt wax ltrate Filtrate-i-oveiead Filtrate-i-overhead-lfrom H. M. Wax ottoms H. M. L. M. Dist. fraction wax dewax dcposition in chg., ailing oiling Deoil- Over- Deoil- Over- Deoil- Overpercent vol. temp., Percent Percent temp., M. P., ing all M. P., ing all M. P., ing all F. of of F. F., yield, yie1d2, F., yield, yield?, F., yield, yield-2,

charge l crude2 ASTM percent percent ASTM percent percent ASTM percent percent vol. vol. vol. vol. vol. vol.

0 110 90 120 91 41 0-87 50 37 32 20 114 77 124 8O 36 40 117 b3 129 68 31 0 110 S0 124 86 40 13-87 40 27 20 20 112 66 127 74 34 40 114 53 132 61 28 0 111 75 125 81 42 26-87 30 22 13 20 113 52 127 64 34 40 115 29 132 48 25 0 109 67 129 84 54 43.5-87 20 17 7 20 111 44 132 72 46 40 113 22 135 58 37 1 Based on distillation traction to initial deoiling.

2 Based on full range crude wax.

It will be seen, as an example, from the above table that wax with a melting point of 119 F. is obtained when the blend of filtrate and 26 percent volume overhead is deoiled at 0 F. Addition of the bottoms 87-100 percent fraction to this blend and deoiling of the mixture results in a wax having a melting point of 125 F. Increasing the percentage of overhead Wax results in a product of higher melting point.

The marked improvement in filtration rate obtained by addition of distillation overhead Wax to the filtrate from solvent deoiling high melt wax is shown by the following comparative examples in which a crude hydrocarbon Wax charge of above-described characteristics was treated under previously described conditions. The wax product in each instance had an identical oil content, i. e., 0.5 percent by weight.

2. In the treatment of crude hydrocarbon wax wherein the wax is distilled into at least two fractions, one fraction containing low melting point wax and a second fraction containing high melting point Wax and each of said fractions is subjected to solvent deoiling to yield a wax and a filtrate, the improvement which comprises admixng the filtrate from deoiling of the high melting point wax with the fraction containing low melting point wax prior to solvent deoiling of the latter.

3. A method for resolving a crude hydrocarbon wax consisting essentially of oil, high melting wax and low melting wax into its components, which comprises distilling the crude wax under non-cracking conditions into two distillate fractions and a bottoms fraction, removing the lower boiling of said distillate fractions as overhead, removing the higher boiling of said distillate fractions, subjecting said higher boiling distillate to solvent deoiling Filtration to yield a high melting point Wax and a iiltrate, admixing Ex. Wax blend ratelbs said filtrate with said overhead and said bottoms fraction ax/ Uw and solvent deoiling the resulting mixture to separate a low melting point wax therefrom. Filtrate from deoiling of l3-87% distillation fraction 10 4' In the trerfltmelt of Crufie hyrcarbon WX Wherem 1 Filtratelfronldsfilmg lf 1-87iffr1sli1lat1irac 15 50 the wax is distilled into various distillate fractions and a cifgpefls t over lea cu Cm Wax bottoms fraction, one of said distillate fractions containing Fitltate trom deoiling 0f 2687% distillation free 6 low melting wax and another of said distillate fractions 1 D. f l 2 Fiiiiiiie fiom deoiling of 87% disiiuiiioii fiiic- .ai Coptamme h1gh mltmg WaX, the Improyement Whlch C9111- girgpelus 026% Overhead cut from Crude Wax prises solvent deoiling the latter fraction to yield a high Fiiirate'froin deoiling or ias-87% annulation 5 50 mmg pOHll/HX and a lraei admlimg Sald filtrate fraction. a Filtrate from deoiiing of 4s.5-s7% animation so W1 5.11? 1% bate fractflon .Contaumgl 0W rlelllllrig Wtx 3 fraction plus O-43.5% overhead cut from crude and lt Sa 1 Ottoms faction an S0 Vegt e0 .mg e Wax chrgeresulting mixture to separate a low melting point wax therefrom.

It is to be understood that the above description is merely illustrative of preferred embodiments of the invention, of which many variations may be made within the scope of the following claims by those skilled in the art without departing from the spirit thereof.

We claim:

l. A method for separating a crude hydrocarbon wax into a high melting parain wax and a low melting parafn wax, which comprises subjecting the crude wax to distillation under non-cracking conditions, removing as over- 5. In the process of distilling a crude hydrocarbon wax under non-cracking conditions wherein overhead distillate of l-ow melting wax components is removed and a separate distillate of high melting wax components is removed and subjected to solvent deoiling, yielding a high melting point wax and a filtrate, the improvement which comprises increasing the rate of filtration of said filtrate upon subsequent solvent deoiling thereof by admixing therewith prior to said deoiling the aforesaid overhead distillate.

References Cited in the file of this patent head, a distillate containing low melting point, low boiling wax, removing as a separate higher boiling distillate, UNITED STATES PATENTS a fraction containing high melting point wax, deoiling 1,927,057 Anderson sept. 19, 1933 the latter fraction by admixing with a solvent miscible 2,457,959 Bowman et al Apr. 19, 1949 with oil but substantially immiscible with wax, chilling 2,670,318 Halamka et al Feb. 23, 1954 2,734,365 Ferris et al Feb. 14, 1956 the resulting mixture and ltering to yield a high melt- 

1. A METHOD FOR SEPARATING A CRUDE HYDROCARBON WAX INTO A HIGH MELTING PARAFFIN WAX AND A LOW MELTING PARAFFIN WAX, WHICH COMPRISES SUBJECTED THE CRUDE WAX TO DISTILLATION UNDER NON-CRACKING CONDITIONS, REMOVING AS OVERHEAD, A DISTILLATE CONTAINING LOW MELTING POINT, LOW BOILING WAS, REMOVING AS A SEPARATE HIGHER BOILING DISTILLATE, A FRACTION CONTAINING HIGH MELTING POINT WAX, DEOILING THE LATER FRACTION BY ADMIXING WITH A SOLVENT MISCIBLE WITH OIL BUT SUBSTANTIALLY IMMISCIBLE WITH WAX, CHILLING THE RESULTING MIXTURE AND FILETEING TO YIELD, A HIGH MELTING POINT PARAFFIN WAX AND A FILTRATE, ADMIXING SAID FILTRATE WITH THE AFOREMENTIONED OVERHEAD AND SOLVENT DEOILING THE RESULTING MIXTURE TO SEPARATE A LOW MELTING POINT PARAFFIN WAX THEREFROM 